Then, I decided to visit the earliest references on the subject, finding a surprising consistency of choices among genes of the same or similar genomes, a very precise bio-system for choosing between codons. I was searching for the reverse translation from proteins to nucleotides in bioinformatics when I read that different organisms often have radically different codon preferences, a fact profoundly affecting their capability to express different proteins ( Wishart and Fortin, 2001). These findings may help to design computational tools to compare human genomes, to determine the exchangeability between compatible codons and amino acids, and for the early detection of incompatible changes leading to hereditary diseases. The human distribution in the third position of most used codons is a 12-8-2, C-G-A, nucleotide ending signature, while the squid distribution in the third position of most used codons was an odd, or uneven, distribution in the third position of its most used codons: 13-6-3, U-A-G, as its nucleotide ending signature. The C/U choice or difference, and the G/A difference in the third nucleotide of the most used codons per amino acid are illustrated by comparing the most used codons per genome in humans and squids. The biosemiotic codon usage of each genomic population or ‘ Theme’ is equated to a ‘ molecular language’. The human codon usage per genome is compared to other organisms such as fruit flies ( Drosophila melanogaster), squid ( Loligo pealei), and many others. The most used codons in man fall almost all the time at the rightmost position, clockwise, ending either in C or in G within the circular genetic code. The most used human codons per amino acid were the ones ending with the three hydrogen bond nucleotides: C for 12 amino acids and G for the remaining 8, plus one codon for arginine ending in A that was used approximately with the same frequency than the one ending in G for this same amino acid (plus *). Here, I demonstrate that when using the conventional or classic circular genetic code, a clearer pattern for the human codon usage per amino acid and per genome emerges. My previous theoretical research shows that the rotating circular genetic code is a viable tool to make easier to distinguish the rules of variation applied to the amino acid exchange it presents a precise and positional bio-mathematical balance of codons, according to the amino acids they codify.
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